Hydroxypivaldehyde (HPA, 3-hydroxy-2,2-dimethylpropanal) is widely used as a starting material for the preparation of various useful products such as neopentyl glycol (NPG, 2,2-dimethyl-1,3-propanediol), ester glycol (HPHP, Hydroxypivalyl Hydroxypivalate), and spiroglycol [SPG, 3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro(5.5)undecane], which are used in lubricants, plastics, surface coatings, surfactants, and synthetic resins. HPA is typically produced by an Aldol condensation of isobutyraldehyde (iHBu) and formaldehyde (HCHO) in the presence of an amine catalyst to form HPA, as depicted in the following Scheme 1:
Scheme 1
Preparation of Hydroxypivaldehyde in an Aldol Condensation

The tertiary amine catalyst systems are usually run with an excessive amount of aldehyde, which enables the reaction to be carried out in a homogeneous reaction mixture. In these processes, the selectivity of Aldol is increased when compared to the alkaline catalyst systems. However, the use of tertiary amine catalysts in Aldol condensations has a problem in that the tertiary amine catalyst reacts with organic acids to form salts. The organic acids are either from the formaldehyde raw material in the form of formic acid or generated via Cannizaaro reaction of aldehydes during the condensation process. These amine salts cannot be separated from the HPA by distillation and are carried on into the hydrogenation reaction. The amine salts deactivate the metal catalyst used in the hydrogenation reaction. In addition, they decompose the Aldol condensation product during the distillation of product at high temperatures. Thus, overall yields are dramatically decreased.